A large-scale database system includes a plurality of databases and a plurality of index servers, in which the databases and index servers are managed in a distributed manner. The databases hold identification information and attribute information of objects to be managed registered therein. The index servers manage index information in which attribute information and identification information are associated with each other by using the attribute information as key information.
When receiving a search request from a search device, an index server obtains identification information corresponding to attribute information serving as key information included in the search request with reference to index information, and transmits the obtained identification information to the search device. The index information needs to be updated by reflecting an update of attribute information. Also, in accordance with the change in the attribute information, index information needs to be newly registered in the index server that manages the changed attribute information.
When attribute information is frequently updated, the index information corresponding thereto imposes a large update load on the database system. When multiple index servers are used for distributed management in order to distribute loads of search and index management, movement of index information between index servers may be necessary, which further increases the update load. Therefore, the amount of communication performed for a process of registering/deleting index information between an index server and a registration server increases.
The related arts include the followings: Japanese Laid-open Patent Publication Nos. 2006-185019, 2007-122302, and 2008-123426.